A combined experimental and quantum chemical (DFT and AIM) study on molecular structure, spectroscopic properties, NBO and multiple interaction analysis in a novel ethyl 4-[2-(carbamoyl)hydrazinylidene]-3,5-dimethyl-1H-pyrrole-2-carboxylate and its dimer

In the present paper, a new ethyl 4-[2-(carbamoyl)hydrazinylidene]-3,5-dimethyl-1H-pyrrole-2-carboxylate (3) has been synthesized and characterized by 1H NMR, UV–Visible, FT-IR and Mass spectroscopy. The formation of the compound and its properties have also been evaluated by quantum chemical calculations using density functional theory (DFT), B3LYP functional and 6-31G(d,p) as basis set. The calculated thermodynamic parameters show that the formation of (3) is an exothermic and spontaneous reaction at room temperature. 1H NMR chemical shifts are calculated using gauge including atomic orbitals (GIAO) approach in DMSO-d6 as solvent. Time dependent density functional theory (TD-DFT) is used to calculate the energy (E), oscillator strength (f) and wavelength absorption maxima (λmax) of various electronic transitions and their nature within the molecule. NBO analysis is carried out to investigate the stabilization energy of various intra and intermolecular interactions in molecular system. The vibrational analysis indicates the formation of dimer in the solid state by intermolecular heteronuclear hydrogen bonding (NH⋯O) and the binding energy of dimer is calculated to be 10.40 kcal/mol, using DFT calculations. Topological parameters at bond critical points (BCP) are calculated to analyze the strength and nature of various types of intra and intermolecular interactions in dimer by Bader’s ‘Atoms in molecules’ AIM theory in detail. The local reactivity descriptors such as Fukui functions ( f k + , f k - ), local softnesses ( s k + , s k - ) and electrophilicity indices ( ω k + , ω k - ) analyses are performed to determine the reactive sites within molecule.